Conventional electronic devices such as a mobile phone, a tablet terminal, a notebook personal computer (PC), a desktop computer, a game machine, and so on include a microprocessor such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), or the like for processing operations.
According to miniaturization of semiconductor manufacturing processes, an increase of mounted peripheral circuits, and demand for low power consumption, such an electronic device equipped with a microprocessor is segmented into dozens of circuit blocks such that a power supply voltage for each circuit block can be independently controlled.
Conventional electronic devices use a power management IC (PMIC) to control dozens of power supply systems corresponding to the dozens of circuit blocks. The PMIC is required to reliably control turning-on/off of dozens of power supplies in accordance with a predetermined sequence.
The following properties are required for PMIC.
(1) Robustness and Stability
The PMIC requires a mechanism which is capable of preventing an external noise or the like from being overshot.
(2) Safety
The PMIC requires an ability to shut down power supply systems autonomously without relying on other devices when it is in an abnormal state.
(3) Power Saving
The PMIC requires the minimum power consumption since it is necessary for the PMIC to operate even when the system shuts down.
However, it was difficult to use a general purpose microcomputer to construct the PMIC meeting these requirements. Therefore, in the related art, in order to meet the requirements for each electronic device, it was necessary to design a dedicated sequencer in a hardware manner each time.
The plurality of power supplies is classified into several rails. Then, the PMIC can turn on/off the rails independently and a state is specified depending on combination of rails which are in the turned-on state. Specifically, in addition to a state where all power supply rails are turned off and a state where all power supply rails are turned on, there exists some intermediate turned-on stages of the plurality of power supply rails.
In some cases, different platforms on which the PMIC is used may provide different states to be used. For example, since the PMIC may take five states, i.e., first to fifth states if there are four power supply rails, only the first state, the third state, and the fifth state may be used on one platform while only the first state, the fourth state and the fifth state may be used on another platform. In this case, in the conventional art, a PMIC corresponding to the one platform was constructed in a hardware manner to support the first, third and fifth states while a PMIC corresponding to another platform was constructed in a hardware manner to support the first, fourth and fifth states. That is, it was necessary to construct different new hardware of the PMIC for different platforms, which might result in very high design costs.
In the conventional art, even on the same platform, if a starting sequence of some power supplies in the same rail was to be changed, significant design change of hardware was unavoidable. Thus, even a slight change required mask modification, which resulted in extended design time.